Method and Apparatus for Use in Wafer Processing

ABSTRACT

In an embodiment a method includes placing a wafer on a receptacle comprising a chuck base, wherein a light port for emitting light from a source of light is an opening located in a surface of the chuck base, and wherein the light port is located underneath the wafer, shining the light from the light port at an edge of the wafer so that light passes by the edge of the wafer and processing the wafer on the receptacle based on the light that passed by the edge of the wafer and that is received by a light sensitive element.

This application is a divisional application of Ser. No. 17/219,351,filed on Mar. 31, 2021, which is a continuation application of U.S.application Ser. No. 16/220,888, filed on Dec. 14, 2018, now U.S. Pat.No. 10/985,041, which issued on Apr. 20, 2021, which is a continuationapplication of U.S. application Ser. No. 14/933,931, filed on Nov. 5,2015, now U.S. Pat. No. 10,186,438, which issued on Jan. 22, 2019, whichapplications are hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method and apparatus for an alignmentof a wafer for processing.

BACKGROUND

According to some solutions, prior to transfer onto a chuck, a wafer ispre-aligned. Then, the wafer is transferred onto a chuck where it isrotated while a radial distance from wafer edge to a center of the chuckis measured. A sequence of these radial measurements is used todetermine a centration of the wafer on the chuck, its translationalposition, and the location of flats or notches on its periphery whichdefines its rotational orientation, herein also referred to a polarposition. The movement of the chuck assures rotational alignment, and amechanism that then transfers the wafer to a workspace compensates forits translational misalignment. In this way, pre-aligners typically areable to align the wafer to within a degree of rotation and a fewthousandths of an inch in translation. Ultimately, pre-alignmentaccuracy in knowing where die are located relies on the precision of thepre-aligner, the precision of the wafer transport mechanism and theprecision with which die are placed on the wafer. With modernphotolithography, device locations can repeat from wafer to wafer towithin a few thousandths of an inch.

SUMMARY

In an aspect, a method is disclosed herein that is provided for use inprocessing a wafer. The method comprises providing the wafer on areceptacle and shining a light on an edge of the wafer. Further, themethod comprises, based on light that passed the edge of the wafer,processing the wafer on the receptacle.

In another aspect, an apparatus for use in processing a wafer isdisclosed. The apparatus comprises a receptacle configured to receivethe wafer during a processing act. The apparatus comprises a lightsensitive element configured to form a detection signal based on lightthat passed by an edge of the wafer to hit the light sensitive element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram that illustrates a sectional side view of aprocessing apparatus according to some embodiments;

FIG. 2 is a diagram that illustrates a flow chart that representing actsperformed in a method according to some embodiments;

FIG. 3A is a schematic representation of an exemplary first image takenin use of a processing apparatus according to some embodiments;

FIG. 3B is a schematic representation of an exemplary second image takenin use of a processing apparatus according to some embodiments;

FIG. 4 is a diagram that illustrates a sectional side view of aprocessing apparatus according to some embodiments;

FIG. 5 is a diagram that illustrates a sectional side view of aprocessing apparatus according to some embodiments;

FIG. 6A is a schematic representation of an exemplary first image takenin use of a variant of a processing apparatus according to someembodiments;

FIG. 6B is a schematic representation of an exemplary second image takenin use of a variant of a processing apparatus according to someembodiments;

FIG. 6C is a schematic representation of an exemplary third image takenin use of a variant of a processing apparatus according to someembodiments;

FIG. 6D is a schematic representation of an exemplary fourth image takenin use of a variant of a processing apparatus according to someembodiments; and

FIG. 7 is a diagram that illustrates a sectional side view of aprocessing apparatus according to some embodiments.

Below, embodiments, implementations and associated effects are disclosedwith reference to the drawings. The elements of the drawings are notnecessarily to scale relative to each other. Like reference numeralsdesignate corresponding similar parts. Because components of embodimentsaccording to the present invention can be positioned in a number ofdifferent orientations, directional terminology may be used for purposesof illustration that, however, is in no way limiting, unless expresslystated to the contrary. Other embodiments according to the presentinvention and many of the intended advantages of the present inventionwill be readily appreciated as they become better understood byreference to the following detailed description. It is to be understoodthat other embodiments may be utilized and structural or logical changesmay be made without departing from the scope of the present invention.The following detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 is a diagram that illustrates a sectional side view of aprocessing apparatus 100 according to some embodiments. Processingapparatus 100 comprises a chuck base 110 and a turntable 120. Processingapparatus 100 comprises a bearing 130 configured to bear turntable 120on chuck base 110. In some embodiments, chuck base 110 has a rim 115that, in some implementations approximately in a plane with a surface121 of turntable 120, surrounds turntable 120.

In some embodiments, processing apparatus 100 comprises a drive unit180. In some implementations, drive unit 180 is configured to receive acontrol signal and, based on the control signal, to move turntable 120.In some embodiments, turntable 120 is provided with a drive unit 180configured to rotate turntable 120 relative to chuck base 110 about adrive rotation axis 135 that, in some embodiments, is essentiallyvertical. In some implementations, drive unit 180 is configured tolaterally move turntable 120 relative to chuck base 110.

Turntable 120 is provided with surface 121 configured to support aworkpiece. A peripheral portion of turntable 120 forms a protrusion 125that partially covers a portion of a peripheral recess 140 provided bychuck base 110. In some embodiments, peripheral recess 140 houses asource of light 145. For example, peripheral recess 140 houses a lightemitting diode.

Further, processing apparatus 100 comprises a camera 160 having a lenssystem 164 with a field of view 166. In some embodiments, an axis oflens system 164 is essentially collinear with drive rotation axis 135.In some implementations, camera 160 comprises an image sensor and isconfigured to output a detect signal representative of light sensed bythe image sensor. In some embodiments, the image sensor is provided as acharge coupled device that is configured to output an image signal as adetect signal.

In some implementations processing apparatus 100 comprises, or iscoupled to, a control unit 170. More particularly, control unit 170 isselectively coupled to other components of processing apparatus 100. Forexample, control unit 170 is coupled, via a detect signal link 168, tocamera 160. In some embodiments, control unit 170 is coupled, via afirst control signal link 171, to source of light 145. Further, in someimplementations, control unit 170 is coupled, via a second controlsignal link 172, to drive unit 180. As will be described in more detailbelow, in some embodiments control unit 170 is configured to receive thedetect signal from camera 160, process the detect signal to derive afirst control signal and to transmit the first control signal to sourceof light 145. In some embodiments, control unit 170 is configured toderive, based on the detect signal, a second control signal and totransmit the second control signal to drive unit 180.

Now, use of processing apparatus 100 according to some implementationswill briefly be described with respect to FIG. 2 which is a diagram thatillustrates a flow chart that represents acts performed in a methodaccording to some embodiments.

At S205, a workpiece is provided on surface 121 of table 120. In someimplementations, the workpiece can, for example, be a wafer 150 such asa silicon wafer that is used in manufacturing semiconductor devices. Insome implementations, an edge portion 155 of wafer 150 can radiallyextend beyond protrusion 125 of turntable 120, while a top surface 157of wafer 150 faces lens system 164 of camera 160.

In some implementations, at S210, drive unit 180 is operated to adjust aposition of turntable 120. In some embodiments, drive unit 180 movesturntable 120 with wafer 150 laterally with respect to chuck base 110.In some implementations, drive unit 180 rotates turntable with wafer 150with respect to chuck base 110.

At S220, control unit 170 controls source of light 145 so as toilluminate peripheral recess 140. Light from source of light 145, somedirectly and some indirectly, in particular by reflection at a wallsurface of peripheral recess 140, illuminates edge portion 155 of wafer150. In particular, however, at least according to some implementations,no, or at least comparatively little, light from source of light 145hits top surface 157 of wafer 150.

At S230, camera 160 detects light, for example, by using the chargecoupled device comprised in camera 160, and outputs an image signal as adetect signal onto detect signal link 168 for transmission to controlunit 170.

At S240, control unit 170 receives the image signal and processes theimage signal. In some implementations, processing of the image signalgenerates at least a first control signal for use in control of lightsource 145. In some implementations, control unit 170 generates thesecond control signal based on the orientation information. In someimplementations, processing of the image signal generates at least asecond control signal for use in control of drive unit 180. In someimplementations, control unit 170 generates the second control signalbased on orientation information about an orientation of wafer 150 aboutdrive rotation axis 135 and relative to chuck base 110.

In some implementations, at S250, control unit 170 transmits the firstcontrol signal, via first control signal link 171, to source of light145. For example, the first control signal can represent a flagindicative of a switch operation such as an instruction to switch onsource of light 145 or an instruction to switch off source of light 145.

In some implementations, at S250, control unit 170 transmits the secondcontrol signal, via second control signal link 172, to drive unit 180.For example, the second control signal can represent a flag indicativeof a switch operation such as an instruction to switch on drive unit 180or an instruction to switch off drive unit 180.

At S260, based on the image signal, according to some implementations,control unit 170 generates position data that represent information on aposition of wafer 150, for example, with reference to chuck base 110. Insome implementations the generating comprises calculation of positioncoordinates and/or angles. In some implementations the generatingcomprises submitting a plurality of measurement data to a statisticalanalysis. Position information, in some embodiments, comprises a lateralposition with respect, for example, to drive rotation axis 135. Positioninformation, in some embodiments, comprises orientation information ofwafer 150 about drive rotation axis 135. In some embodiments, positioninformation comprises both, lateral position and rotational position. Insome implementation, the position information is used in order to alignany tool or mask according to the position of wafer 150, for example,for use in subsequent wafer processing acts.

It should be understood that a sequence of acts described above withrespect to FIG. 2 can be different according to differentimplementations. For example, in some implementations, act S260 isperformed prior to some or all of act S250, i.e., prior to transmissionof the first control signal from control unit 170 to the source of light145 and/or prior to transmission of the second control signal fromcontrol unit 170 to drive unit 180.

In some implementations, some of the acts described above with referenceto FIG. 2 are essentially performed simultaneously. For example, in someimplementations, once the source of light 145 is switched on, at leastduring an interval of time used for alignment of wafer 150, act S220 iscontinuously performed, i.e., wafer 150 is continuously illuminated. Atthe same time, light is continuously detected, i.e., act S230 iscontinuously performed. In some implementations, control unit 170receives a stream of data representing an image signal that represents asequence of images. In some embodiments, control unit 170, for eachimage, generates the first and/or the second control signal. Thus, ineffect, act S240 is continuously performed. In some implementations,control unit 170 essentially continuously transmits the first and/or thesecond control signal, whereby act S250 is essentially continuouslyperformed. In some implementations, position data are continuouslygenerated, i.e., some or all of act S260 is continuously performed. Inother implementations, a plurality of alignment intervals is used toperform at least some of the above-described acts simultaneously atleast during selected intervals of the plurality of alignment intervals.An interval length, in some embodiments, is predetermined. In someembodiments, the length of the interval is flexible. For example, insome embodiments the interval ends after a predetermined criteria ismet. In some implementations, for example, the predetermined criteria isan error in position measurement resulting from a statistical analysisof data points generated by previous measurements having fallen below apredetermined error interval.

FIG. 3A is a schematic representation of an exemplary first image seenin use of processing apparatus 100 according to some embodiments. Thefirst image, in some implementations could, for example, be taken bycamera 160 during an interval, when, at S220, source of light 145 isswitched on to illuminate peripheral recess 140 of chuck base 110. Lightfrom source of light 145 gets reflected by the wall surface ofperipheral recess 140 and illuminates edge portion 155 of wafer 150 tothrow a shadow. Thus, in some implementations, for lack of any othersource of light, wafer 150 throws a shadow that, in the first imagedetected at camera 16 o, appears as a dark field 350. However, somelight from source of light 145 gets reflected by the wall surface ofperipheral recess 140 to then pass edge portion 155 of wafer 150 and hitlens system 164 of camera 160 where, in some implementations, the lighthits a charge coupled device or other light sensitive element. Thecharge coupled device thus detects light that passed wafer 150, whereinthe detected light forms an image of a bright ring 340. Further, forlack of any illumination of a top surface of rim 115, rim 115, at camera160 is seen as a dark ring 315 that surrounds bright ring 340 and darkfield 350 and whose diameter fits within the field of view 166 of camera160.

Still looking at FIG. 3A, a co-ordinate system having orthogonal axes301 and 302 is shown that is concentric to dark ring 315, i.e., theshadow associated with chuck rim 115. A contrast between light thatpassed edge portion 155 of wafer 150 and a shadow thrown by wafer 150,in particular by edge portion 155 of wafer 150, is particular sharp. Atleast one effect is that a position of wafer 150 relative to a rim 115of chuck base 110, based on the first image, can be determined moreprecisely than in a case where a top surface of wafer 150 is illuminatedin order to detect light reflected from the top surface. In a case,where wafer 150 lacks rotational symmetry, for example, in the casedepicted in FIG. 3A, where wafer 150 is of essentially circular shapewhose rotational symmetry, albeit, is broken by a flat, based on thefirst image detected at camera 160, a rotational position of wafer 150can also more precisely be determined. The flat is identified preciselyat a correspondingly “flat” portion 342 of bright ring 340 where a widthof bright ring 340 with changing polar angle characteristically firstrises to a maximum width and then falls. In some embodiments, processingof data of the first image can generate control signals for use incontrol, for example, of drive unit 180.

FIG. 3B is a schematic representation of an exemplary second image seenin use of processing apparatus 100 according to some embodiments. Moreparticularly, in some implementations, drive unit 180 receives thecontrol signals and accordingly moves turntable 120 into a predeterminedalignment position where wafer 150 is positioned, for example, with acentre on-axis with drive rotation axis 135. Further, the flat can berotated into a predetermined position, for example, as in the exampleshown in FIG. 3B, into a “3o'clock position”. As described above, insome embodiments camera 160 takes a plurality of images and submitsimage data that represent the image to control unit 170 for processing.In some implementations, for example, at a time, for example, when anerror of position has fallen below a predetermined error ceiling,control unit 170 provides a switch off signal to source of light 145and/or to camera 160 to end alignment of wafer 150. In someimplementations, apparatus 100 then proceeds to work wafer 150. Forexample, apparatus 100 sets a cutting tool to wafer 150 so as to cut ofburr from wafer edge 155. For another example, apparatus 100 sets acutting tool to wafer 150 so as to cut away a lost carrier ring fromwafer edge 155. The position of wafer 150 and/or the orientation ofwafer 150 relative to chuck base 110, in other words the rotationalposition of wafer 150, are determined and, in some embodiments, thewafer is also aligned according to some implementations in accordancewith predetermined alignment requirements. At least one effect accordingto some embodiments is pre-alignment of wafer 150 can be omitted. Thus,time may be saved. Also, space may be saved since, at least in someimplementations, a pre-alignment tool may not be needed. This effect canbe of particular importance since wafer processing typically takes placein a clean room where space is scarce.

It should be understood that the positions and shapes described herein,meanwhile, are merely to state an example. Neither does the shape of thewafer need to be essentially circular, nor do the positions need to beselected as described herein. For example, the wafer could have arectangular shape or an arbitrary shape that does not correspond to anysimple geometrical shape such as rectangle, triangle and circle. Aposition of a centre such as a “weight” centre of wafer 150 could bepredetermined to be located out of axis from drive rotation axis 135. Inaccordance with the concept underlying the techniques disclosed herein,however, at least three portions of edge 155 of wafer 150 are providedabove recess 140 to detect a corresponding shadow that fits a contour ofwafer 150 and, in some implementations, enables a calculation of aposition of wafer 150 that is consistent, in some cases uniquelyconsistent, with the detected image.

FIG. 4 is a diagram that illustrates a sectional side view of aprocessing apparatus 400 according to some embodiments. Processingapparatus 400 comprises a chuck base 410 and a pillar field 420. Pillarfield 420 comprises a plurality of pillars 421 in a space 425 abovefield floor 430. In some embodiments, pillars 421 are approximatelyevenly spaced apart from one another. In some embodiments, pillars 421have, at a top, a tip 422 configured to support a workpiece. In someimplementations, pillars 421 of pillar field 420 are provided such thattip 422 of each pillar 421 is located in a common plane. In someimplementations the plane is horizontal. At least one effect is that aflat workpiece such as a wafer 450 can be evenly supported on pillars421 of pillar field 420. In some implementations, pillars 421 areprovided with an opening (now shown) in tip 422 that is coupled to apressure unit (not shown) configured to vary a pressure at the opening.At least one effect can be that a workpiece such as a wafer 450, byapplying a low pressure, can be sucked towards pillars 421, whereby aresistance, for example, against lateral movement of wafer 450, isincreased. At least one other effect can be that a workpiece such aswafer 450, by applying a high pressure, can be lifted above pillars 421,whereby a pickup of the wafer 450 and/or lateral movement of wafer 450may be facilitated. In a variant (not illustrated), instead of thepillar field, the processing apparatus can comprise a table similar totable 120 of processing apparatus 100 illustrated in FIG. 1 , but havingopenings in a surface coupled to a pressure system configured toselectively apply a high pressure and low pressure, whereby a workpieceprovided atop the table is either sucked to the table or lifted abovethe table.

In some embodiments, pillar field 420 comprises at least one source oflight 445. For example, pillar field 420 comprises a light emittingdiode. In some embodiments (not shown), selected pillars 421 of pillarfield 420 include the source of light. In some implementations, allpillars 421 of pillar field 420 include a respective source of light445.

Further, processing apparatus 400 comprises a camera 460 having a lenssystem 464 with a field of view 466. In some embodiments, an axis 435 oflens system 464 is essentially perpendicular to a plane common to tips422 of pillars 421. In some implementations, camera 460 comprises animage sensor and is configured to output a detect signal representativeof light sensed by the image sensor. In some embodiments, the imagesensor is provided as a charge coupled device that is configured tooutput an image signal as a detect signal.

In some implementations processing apparatus 400 comprises, or iscoupled to, a control unit (not shown). More particularly, the controlunit is selectively coupled to other components of processing apparatus400. For example, the control unit may be coupled, via a detect signallink, to camera 460. In some embodiments, the control unit is coupled,via a first control signal link, to source of light 445. Further, insome implementations, the control unit is coupled, via a second controlsignal link, to the pressure unit. In some embodiments, the control unitis configured to receive the detect signal from camera 460, process thedetect signal to derive a first control signal and to transmit the firstcontrol signal to source of light 445. In some embodiments, the controlunit is configured to derive, based on the detect signal, a secondcontrol signal and to transmit the second control signal to the pressureunit.

In some implementations, operation of processing apparatus 400, inessence, is performed similar to operation of processing apparatus 100.However, instead of operating a drive unit, in processing apparatus 400the pressure unit is operated in order to provide a low pressure wherebywafer 450 is affixed atop pillars 421 of pillar field 420. Further thepressure unit is operated to release wafer 450 from a fixation atoppillars 421 so as to enable a removal of wafer 450 from processingapparatus 400. Use of processing apparatus 400 according to someimplementations will briefly be described, again with reference to FIG.2 .

At S205, a workpiece is provided on pillars 421 of pillar field 420. Insome implementations, the workpiece can, for example, be a wafer 450such as a silicon wafer that is used in manufacturing semiconductordevices. In some implementations, an edge portion 455 of wafer 450radially extends above a part of space 425 provided with pillars 421,while a top surface 457 of wafer 450 faces lens system 464 of camera460.

In some implementations, at S210, the pressure unit is operated toprovide a low pressure and, thus, to affix wafer 450 in a positionrelative to chuck base 410.

At S220, the control unit controls source of light 445 so as toilluminate pillar field 420 in the space 425 provided between pillars421. Light from source of light 445, some directly and some indirectly,in particular by reflection at a wall surface of a peripheral portion440 of chuck base 410, illuminates edge portion 455 of wafer 450. Inparticular, however, at least according to some implementations, no, orat least comparatively little, light from source of light 445 hits topsurface 457 of wafer 450.

At S230, camera 460 detects light, for example, by using the chargecoupled device comprised in camera 460, and outputs an image signal as adetect signal onto the detect signal link for transmission to thecontrol unit (not shown in FIG. 4 ).

At S240, the control unit receives the image signal and processes theimage signal. In some implementations, processing of the image signalgenerates at least a first control signal for use in control of lightsource 445. In some implementations, the control unit generates thesecond control signal based on the orientation information. In someimplementations, processing of the image signal generates at least asecond control signal for use in control of the pressure unit. In someimplementations, the control unit generates the second control signalbased on orientation information about an orientation of wafer 450 aboutan axis that, for example, meets a centre of wafer 450 and is parallelto axis 435 of lens system 464 and relative to chuck base 410.

In some implementations, at S250, the control unit transmits the firstcontrol signal, via the first control signal link, to source of light445. For example, the first control signal can represent a flagindicative of a switch operation such as an instruction to switch onsource of light 445 or an instruction to switch off source of light 445.

In some implementations, at S250, the control unit transmits the secondcontrol signal, via the second control signal link, to the pressureunit. For example, the second control signal can represent a flagindicative of a switch operation such as an instruction to switch onpressure unit, for example, to create a low pressure whereby wafer 450is affixed atop pillar field 420, or an instruction to switch offpressure unit, for example, to create a high pressure, whereby wafer 450is released from pillar field 420.

At S260, based on the image signal, according to some implementations,the control unit generates position data that represent information on aposition of wafer 450, for example, with reference to chuck base 410. Insome implementations the generating comprises calculation of positioncoordinates and/or angles. In some implementations the generatingcomprises submitting a plurality of measurement data to a statisticalanalysis. Position information, in some embodiments, comprises a lateralposition with respect, for example, to axis 435 of lens system 464.Position information, in some embodiments, comprises orientationinformation of wafer 450 about lens axis 435. In some embodiments,position information comprises both, lateral position and rotationalposition. In some implementation, the position information is used inorder to align any tool or mask according to the position of wafer 450,for example, for use in subsequent wafer processing acts.

As described above, FIG. 3A is a schematic representation of anexemplary image seen in use of processing apparatus 400 according tosome embodiments. The image, in some implementations could, for example,be taken by camera 460 during an interval, when, at S220, source oflight 445 is switched on to illuminate peripheral portion 440 of chuckbase 410. Light from source of light 445 gets reflected by the wallsurface of peripheral portion 440 of chuck base 410 and illuminates edgeportion 455 of wafer 450 to throw a shadow. Thus, in someimplementations, for lack of any other source of light, wafer 450 throwsa shadow that, in the image detected at camera 460, appears as a darkfield 350. However, some light from source of light 445 gets reflectedby the wall surface of peripheral portion 440 to then pass edge portion455 of wafer 450 and hit lens system 464 of camera 460 where, in someimplementations, the light hits a charge coupled device or other lightsensitive element. The charge coupled device thus detects light thatpassed wafer 450, wherein the detected light forms an image of a brightring 340. Further, for lack of any illumination of a top surface of rim415, rim 415, at camera 460 is seen as a dark ring 315 that surroundsbright ring 340 and dark field 350 and whose diameter fits within thefield of view 466 of camera 460. At least one effect can be that, asdescribed in more detail above with reference to FIG. 3A, a position ofwafer 450 can be well determined, since the image taken by camera 460has a high contrast of a shadow thrown by wafer 450 against light fromsource of light 445 provided in pillar field 420 below wafer 460.Accordingly, a tool for use in further working the wafer, for example,to cut away an edge portion of wafer 450, can be precisely set to wafer460.

FIG. 5 is a diagram that illustrates a sectional side view of aprocessing apparatus 500 according to some embodiments. Processingapparatus 500 closely resembles processing apparatus 100 described abovewith reference to FIG. 1 . More particularly, processing apparatus 500comprises a chuck base 510 and a turntable 520. Processing apparatus 500comprises a bearing 530 configured to bear turntable 520 on chuck base510. In some embodiments, chuck base 510 has a rim 515 that, in someimplementations approximately in a plane with a surface 521 of turntable520, surrounds turntable 520.

In some embodiments, processing apparatus 500 comprises a drive unit580. In some implementations, drive unit 580 is configured to receive acontrol signal and, based on the control signal, to move table 520. Insome embodiments, turntable 520 provided with drive unit 580 isconfigured to rotate table 520 relative to chuck base 510 about a driverotation axis 535. In some implementations, drive unit 580 is configuredto laterally move table 520 relative to chuck base 510.

Table 520 is provided with a surface 521 configured to support aworkpiece. A peripheral portion of turntable 520 forms a protrusion 525that partially covers a peripheral recess 540 provided by chuck base510. In some embodiments, peripheral recess 540 houses a source of light545. For example, peripheral recess 540 houses a light emitting diode.

Further, processing apparatus 500 comprises a camera 560 having a lenssystem 564 with a field of view 566. In some embodiments, an axis 565 oflens system 564 is essentially perpendicular to chuck base 510 and meetsperipheral recess 540. In some implementations, camera 560 comprises animage sensor and is configured to output a detect signal representativeof light sensed by the image sensor. In some embodiments, image sensoris provided as a charge coupled device that is configured to output animage signal as a detect signal.

In some implementations, processing apparatus 500 comprises, or iscoupled to, a control unit 570. More particularly, control unit 570 isselectively coupled to other components of processing apparatus 500. Forexample, control unit 570 is coupled, via a detect signal link 568, tocamera 560. In some embodiments, control unit 570 is coupled, via afirst control signal link 571, to source of light 545. Further, in someimplementations, control unit 570 is coupled, via a second controlsignal link 572, to drive unit 580. As will be described in more detailbelow, in some embodiments control unit 570 is configured to receive thedetect signal from camera 560, process the detect signal to derive afirst control signal and to transmit the first control signal to sourceof light 545 In some embodiments, control unit 570 is configured toderive, based on the detect signal, a second control signal and totransmit the second control signal to drive unit 580.

Now, use of processing apparatus 500 according to some implementationswill briefly be described, again, with respect to FIG. 2 . It should beunderstood that the techniques of use described above with reference toprocessing apparatus 100 illustrated FIG. 1 and with reference to actsdisclosed in the flow chart shown in FIG. 2 can essentially also appliedto of processing apparatus 500 that is schematically depicted in FIG. 5.

At S205, a workpiece is provided on surface 521 of table 520. In someimplementations, the workpiece can, for example, be a wafer 550 such asa silicon wafer that is used in manufacturing semiconductor devices. Inan exemplary embodiment, wafer 550 has an essentially circular shapewhose rotational symmetry is broken by a wafer flat. In someimplementations, an edge portion 555 of wafer 550 can radially extendbeyond protrusion 525 of turntable 520, while an edge of top surface 557of wafer 550 faces lens system 564 of camera 560.

In some implementations, at S210, drive unit 580 is operated to adjust aposition of turntable 520. In some embodiments, drive unit 580 movesturntable 520 with wafer 550 laterally with respect to chuck base 510.In some implementations, drive unit 580 rotates turntable with wafer 550with respect to chuck base 510.

At S220, control unit 570 controls source of light 545 so as toilluminate peripheral recess 540. Light from source of light 545, somedirectly and some indirectly, in particular by reflection at a wallsurface of peripheral recess 540, illuminates edge portion 555 of wafer550. In particular, however, at least according to some implementations,no, or at least comparatively little, light from source of light 545hits top surface 557 of wafer 550.

At S230, camera 560 detects light, for example, by using the chargecoupled device comprised in camera 560, and outputs an image signal as adetect signal onto detect signal link 568 for transmission to controlunit 570.

At S240, control unit 570 receives the image signal and processes theimage signal. In some implementations, processing of the image signalgenerates at least a first control signal for use in control of lightsource 545. In some implementations, control unit 570 generates thesecond control signal based on the orientation information. In someimplementations, processing of the image signal generates at least asecond control signal for use in control of drive unit 580. In someimplementations, control unit 570 generates the second control signalbased on orientation information about an orientation of wafer 550 aboutdrive rotation axis 535 and relative to chuck base 510.

In some implementations, at S250, control unit 570 transmits the firstcontrol signal, via first control signal link 571, to source of light545. For example, the first control signal can represent a flagindicative of a switch operation such as an instruction to switch onsource of light 545 or an instruction to switch off source of light 545.

In some implementations, at S250, control unit 570 transmits the secondcontrol signal, via second control signal link 572, to drive unit 580.For example, the second control signal can represent a flag indicativeof a switch operation such as an instruction to switch on drive unit 580or an instruction to switch off drive unit 580.

At S260, based on the image signal, according to some implementations,control unit 570 generates position data that represent information on aposition of wafer 550, for example, with reference to chuck base 510. Insome implementations the generating comprises calculation of positioncoordinates and/or angles. In some implementations the generatingcomprises submitting a plurality of measurement data to a statisticalanalysis. Position information, in some embodiments, comprises a lateralposition with respect, for example, to drive rotation axis 535. Positioninformation, in some embodiments, comprises orientation information ofwafer 550 about drive rotation axis 535. In some embodiments, positioninformation comprises both, lateral position and rotational position. Insome implementation, the position information is used in order to alignany tool or mask according to the position of wafer 550, for example,for use in subsequent wafer processing acts.

As discussed above with reference to FIG. 2 , it should be understoodthat a sequence of acts described above with respect to FIG. 2 can bedifferent according to different implementations. Further, in someimplementations, some of the acts described above with reference to FIG.2 are essentially performed simultaneously.

FIG. 6A is a schematic representation of an exemplary first image takenin use of a variant of a processing apparatus according to someembodiments. The first image, in some implementations could, forexample, be taken by camera 560 during an interval, when, at S220,source of light 545 is switched on to illuminate peripheral recess 540of chuck base 510. In contrast to images discussed above with referenceto FIG. 3A and FIG. 3B, where the field of view 166 of camera 160covered all of wafer 150, peripheral recess 140 and at least a portionof rim 115, the field of view 566 of camera 560 covers merely a sectionof an edge portion of wafer 550, peripheral recess 540 and rim 515.

Light from source of light 545 gets reflected by the wall surface ofperipheral recess 540 and illuminates edge portion 555 of wafer 550 tothrow a shadow. Thus, in some implementations, for lack of any othersource of light, wafer 550 throws a shadow that, in the first imagedetected at camera 560, appears as a dark field 650. However, some lightfrom source of light 545 gets reflected by the wall surface ofperipheral recess 540 to then pass edge portion 555 of wafer 550 and hitlens system 564 of camera 560 where, in some implementations, the lighthits a charge coupled device or other light sensitive element. Thecharge coupled device thus detects light that passed wafer 550, whereinthe detected light forms an image of a bright portion 640 of anillumination ring. Further, for lack of any illumination of a topsurface of rim 515, a portion of rim 515, at camera 560 is seen as adark portion 615 of a ring adjacent to bright portion 640 of theillumination ring and dark field 650.

The exemplary first image also shows a wafer flat 652. Thus, the firstimage includes sufficient information for control unit 570 to calculatea position of wafer 450 relative to chuck base 510.

FIG. 6B is a schematic representation of an exemplary second image takenin use of a variant of a processing apparatus according to someembodiments. In some implementations, between taking the first imageshown in FIG. 6A and taking the second image shown in FIG. 6B, wafer 550is rotated about drive rotation axis 535. Thereby, flat 652 was movedout of field of view 566 of camera 560. Unless wafer 550 is positionedconcentrically on turntable 520, a radial distance varies. This is shownin FIG. 6B where, a line is drawn in a direction 612 that isperpendicular to a tangent 611 of wafer shadow 650. The varying distancedepends on the position of wafer 550 on turntable 520. Given information on a polar position of turntable 520 relative to chuck base510 at the time of taking the second image, using the second image,control unit 570 can thus determine the position of wafer 550 onturntable 520. Further images taken by camera 560 with turntable 520 atother polar angles about drive rotation axis 535 can be used to increasea precision of the calculation of the position of wafer 550 on turntable520. For example, FIG. 6C is a schematic representation of an exemplarythird image taken in use of a variant of a processing apparatusaccording to some embodiments, and FIG. 6D is a schematic representationof an exemplary fourth image taken in use of a variant of a processingapparatus according to some embodiments, wherein, in FIG. 6D flat 652is, again, visible, since wafer 550 was rotated sufficiently far to moveflat into the field of view of camera 560.

FIG. 7 is a diagram that illustrates a sectional side view of aprocessing apparatus according to some embodiments. Processing apparatus700 comprises a chuck base 710 having a chuck table 720 with a tablesurface 721 configured to support a workpiece such as a wafer 750 (shownin FIG. 7 in the process of being set down, indicated by arrows 735,onto the table surface 721). In some embodiments, chuck base 710 has arim 715. In some implementations, rim 715 is set lower than the tablesurface 721. In some implementations (not shown in FIG. 7 ), rim 715surrounds table 720 approximately in a plane with the table surface 721.

A peripheral portion of chuck table 720 is provided with a recess 740.In some embodiments, peripheral recess 740 surrounds all of chuck table720. In some embodiments, peripheral recess 740 is provided merely atselected rotational positions or angles as seen from a centre of thetable surface 721. In some embodiments, peripheral recess 740 receives asource of light 745. For example, peripheral recess 740 houses afluorescent tape and/or an organic light emitting diode foil as thesource of light 745. In some embodiments, a light emitting surface 746of the source of light 745 aligns to and/or is provided in a plane withthe table surface 721.

Further, processing apparatus 700 comprises or can be coupled to acamera 760 with a field of view 766 (not drawn to scale). Someembodiments of camera 760 comprise a lens system 764. In someembodiments, an axis 765 of lens system 764 is essentially perpendicularto table surface 721. In some implementations, camera 760 comprises animage sensor and is configured to output a detect signal representativeof light sensed by the image sensor. In some embodiments, the imagesensor is provided as a charge coupled device that is configured tooutput an image signal as a detect signal.

In some embodiments, processing apparatus 700 comprises a drive unit(not shown) configured to receive a control signal and, based on thecontrol signal, to move camera 760 above chuck base 710, in particularabove chuck table 720 as is indicated in FIG. 7 by arrows 736 and 737that, however, are only indicative of motion as such while a directionof motion relative to chuck surface 720 is inaccurately represented. Itshould be noted that, in some implementations, the motion of camera 760,is essentially in a plane parallel to chuck surface 720. In someembodiments, camera 760 can be configured to rotate relative to chuckbase 710 about a rotational axis approximately perpendicular to tablesurface 720 and, in some implementations, approximately meeting acentral portion of table surface 720 (for example, in FIG. 7 , wherearrows 735 are drawn). Camera 760 is thus configured to move relative tochuck base 710 and chuck table 720.

In some implementations, processing apparatus 700 comprises, or iscoupled to, a control unit 770. More particularly, control unit 770 isselectively coupled to other components of processing apparatus 700. Forexample, control unit 770 is coupled, via a detect signal link 768, tocamera 760. In some embodiments (not shown in FIG. 7 ), control unit 770is coupled, via a first control signal link, to source of light 745.Further, in some implementations, control unit 770 is coupled, via asecond control signal link 771 to camera 760. In some embodimentscontrol unit 770 is configured to receive the detect signal from camera760, process the detect signal to derive a first control signal and totransmit the first control signal to source of light 745. In someembodiments, control unit 770 is configured to derive, based on thedetect signal, a second control signal and to transmit the secondcontrol signal to camera 760. In some embodiments the control unit 770is operative to control motion of the camera 760 above the table surface721 supporting the wafer 750. In particular, control unit 770 can beoperative to control a drive unit (not shown) so as to drive camera 760to predetermined locations such that the light emitting surface 746 ofthe source of light 745 is at least partially in the field of view 766of camera 760. Thus, an edge of wafer 750 put down on the chuck table'ssurface 721 can be inspected by camera 760 using light emitted from thesource of light 745 at various portions of the chuck table 720 andpassing an edge of the wafer 750 as described above with respect, forexample, to embodiments illustrated in FIGS. 1, 4 and 5 .

It should be understood that in accordance with the present disclosurethe level of precision in determining the position of the workpiece onthe chuck can be particularly high because of the contrast betweenbacklight provided by the source of light essentially covered by theworkpiece and light radiated from the source of light that passed theworkpiece before hitting the camera or other image detector, however,without having been reflected by the surface of the workpiece to theextent that the surface provides a portion of the image “seen” by thecamera.

Other embodiments are possible, in order to implement the concepts andtechniques disclosed herein. For example, the person skilled in the artcan provide a chuck configured to affix a wafer on the chuck, similar toembodiments discussed above with reference to FIG. 4 , and provide acamera and/or other light sensitive device movably facing the chuck, inparticular to track an edge portion of a wafer affixed to the chuck.

In an aspect the invention encompasses a method for use in handling awafer, in particular, for use in processing the wafer. The methodcomprises providing the wafer on a receptacle such as a chuck, shining alight at an edge of the wafer, and, based on light that passed the edgeof the wafer, processing the wafer on the receptacle. In someimplementations, the edge of the wafer comprises an edge formed by ahole in the wafer and, thus, surrounded by the wafer. At least oneeffect can be that the light passing by the edge of the wafer is notreflected by a surface of the wafer. Therefore, the surface of the waferis essentially kept from affecting the detected light. The less light isreflected by the surface of the wafer, the larger is a contrast in animage taken of an edge portion of the wafer, where light that passed theedge contrasts with a shadow thrown by the wafer edge portion. The imagecan be used to measure the wafer. For example, in a case where the waferhas an essentially circular shape, a centre can be determined. In a casewhere the wafer is not circular but has another shape, for example, arectangular shape such as a quadratic shape, a trapezoid shape, atriangular shape or another geometric shape, or a complex or anarbitrary shape, for example, a weight centre and/or a boundary lengthcan be determined. Information gathered by analysis of the image can beused in processing the wafer, wherein processing includes one or moreacts in a group of acts comprising: lithography, inking, laminating,mounting, thinning, cutting, optical inspection.

Some embodiments comprise using a light sensitive element to detectlight that passed the edge of the wafer to form a detection signal. Someembodiments comprise controlling, based on the detection signal, aposition of the wafer relative to the receptacle. Some embodimentscomprise deriving, from the detection signal, position informationrepresentative of the position of the wafer relative to the receptacle.Some embodiments comprise, based on the detection signal, generatingposition information representative of a position of the wafer on thereceptacle. Some embodiments comprise using the position information tocontrol alignment of a processing tool.

In some embodiments the shining the light comprises reflecting the lightat a surface of the receptacle prior to passing the light by the edge ofthe wafer. At least one effect can be that a source of light does notneed to be exposed to a tool such as a laser beam that is used to workthe edge of the wafer, for example, to cut the wafer.

Some embodiments comprise operating a light emitting diode to shine thelight. Some embodiments comprise varying a wavelength of the light. Atleast one effect can be that a contrast between light and shadow can bedetected more precisely. In some embodiments the method comprises movingthe detector while keeping the wafer fixed. Some embodiments compriselifting the wafer above the receptacle. Some embodiments compriseshining the light from below the wafer.

In some embodiments the receptacle is provided as a plate such as asupport table of a chuck. At least one effect can be that the wafer canbe submitted to lateral displacement and/or rotation in a plane withoutchanging a vertical distance between an edge surface portion of the workpiece with respect to at least on of the following: the source of light,the detector and a tool configured to work the wafer.

In some embodiments the plate extends above a peripheral recess toaccept a source of light. At least one effect can be that the source oflight can be provided and/or configured to shine into the recess. Insome embodiments the providing the wafer comprises positioning the waferon the plate, for example, in accordance to a predetermined positioninformation. In some embodiments, the predetermined position informationcomprises a central location of the wafer on the plate. In someimplementations the wafer is positioned, for example, so as to extendbeyond the edge of the plate. At least one effect can be that the sourceof light can be configured to shine light so as to pass by the edge ofthe wafer.

In some embodiments a surface of the plate is provided with a recessthat includes a source of light. In some embodiments the providing thewafer comprises positioning the wafer so that an edge of the waferextends over a portion of the recess. In some implementations, at leasta portion of the receptacle is transparent and the source of light isprovided so as to shine through the transparent portion of thereceptacle onto the edge of a wafer supported by the receptacle. In someembodiments, the receptacle is provided with an opening and the sourceof light is provided so as to shine through the opening onto the edge ofa wafer supported by the receptacle.

In some embodiments, for example, rather than providing the source oflight with the receptacle, the source of light is attached to the wafer.In some embodiments at least an edge portion of wafer is provided with asubstrate such as a carrier foil that is configured to emit light. Forexample, in some implementations a fluorescent foil or an organic lightemitting diode foil is attached to the wafer, for example, to provide acarrier for the wafer. In use, seen form an image taking device facingan edge portion the wafer, the light from the foil appears from behindthe wafer and thus provides for a high contrast image.

In some implementations, the receptacle comprises a turntable of a chuckand the method includes rotating the turntable relative to a chuck base.In some implementations, the method comprises moving a spatial field ofview of the light sensitive element and the wafer relative to oneanother. In some embodiments the method comprises rotating the waferwhile keeping the spatial field of view of the detector fixed. At leastone effect can be that a movement of the wafer, e.g., the wafer, aboutits centre can be accomplished with high accuracy. In some embodimentsthe wafer has a circular shape apart from a portion of the wafer, forexample, a wafer flat or a notch, where the edge of the wafer recedesinside a circle defined by the circular shape. Some embodiments comprisealigning the wafer responsive to position information and cutting thewafer.

In another aspect the invention encompasses an apparatus for use inprocessing a wafer. The apparatus comprises a receptacle configured toreceive the wafer during a processing act. Some embodiments comprise alight sensitive element configured to form a detection signal based onlight that passed the edge of the wafer to hit the light sensitiveelement. Some embodiments comprise a light port configured to couple toa source of light and to shine light of the source of light at an edgeof the wafer. In some implementations the receptacle is provided as achuck having an essentially fixed chuck base and a support table orsupport plate. In some implementations the support table is movable. Forexample, the support plate can be provided as a turntable.

Some embodiments comprise a control unit configured to control, based onthe detection signal, a position of the wafer relative to a fixedportion of the receptacle such as a chuck base. In some embodiments thecontrol unit is configured to derive, based on the detection signal,position information representative of the position of the waferrelative to the receptacle. In some embodiments the control unit isconfigured to control an alignment of the wafer responsive to positioninformation. At least one effect can be that the wafer can be alignedfor accurate cutting of the wafer, for example, to cut away an edge ofthe wafer. In some embodiments the control unit is configured to arotationally align a wafer that has a circular shape apart from aportion of the wafer where the edge of the wafer recedes inside a circledefined by the circular shape. In some embodiments, the control unit isconfigured to derive, based on the detection signal, positioninformation representative of the position of the wafer relative to thereceptacle. Some embodiments comprise a drive unit configured to move,for example, to rotate the plate while keeping a spatial field of viewof the detector fixed, wherein the control unit is configured to controlthe drive unit. In some embodiments, the apparatus is configured to movethe light sensitive element relative to the receptacle.

In some embodiments the receptacle is provided as a plate. In someembodiments the plate has planar surface. In some embodiments the plateextends above a peripheral recess configured to house the source oflight. At least one effect can be that the wafer can be positioned onthe plate so as to extend beyond the edge of the plate. In someembodiments a surface of the plate is provided with a recess thatincludes the source of light. At least one effect can be that the wafercan be positioned on the plate so that an edge of the wafer extends overa portion of the recess. In some embodiments the drive unit isconfigured to rotate the plate while keeping a spatial field of view ofthe detector fixed. At least one effect can be that the wafer can be awafer essentially having a circular shape.

In some embodiments the receptacle comprises a surface configured toreflect the light from the light port prior to passing the light by theedge of the wafer. For example, where the receptacle comprises a chuckbase, the chuck base can be provided with a reflective portionconfigured to reflect light prior to the light passing a wafer supportedby the chuck's support table. In some embodiments the light portcomprises a light emitting diode as source of light operative to shinethe light. In some embodiments the light port is configured to vary awavelength of the light shone on the edge of the wafer.

Some embodiments comprise a drive unit configured to move the detectorwhile keeping the wafer fixed.

In another aspect the invention encompasses a computer readable mediumstoring instruction code thereon that, when executed, causes one or moreprocessors to perform acts of a method for use in handling a wafer. Themethod comprises providing the wafer at a receptacle, shining a light atan edge of the wafer, and using a light sensitive element to detectlight that passed by the edge of the wafer to form a detection signal.In some embodiments the medium comprises code to cause control of analignment of the wafer responsive to position information derived fromthe detection signal.

As used herein, like terms refer to like elements throughout thedescription. It is to be understood that the features of the variousembodiments described herein may be combined with each other, unlessspecifically noted otherwise. Although specific embodiments have beenillustrated and described herein, it will be appreciated by those ofordinary skill in the art that a variety of alternate and/or equivalentimplementations may be substituted for the specific embodiments shownand described without departing from the scope of the present invention.This application is intended to cover any adaptations or variations ofthe specific embodiments discussed herein. It is intended that thisinvention be limited only by the claims and the equivalents thereof.

The implementations herein are described in terms of exemplaryembodiments. However, it should be appreciated that individual aspectsof the implementations may be separately claimed and one or more of thefeatures of the various embodiments may be combined. Exemplaryimplementations/embodiments discussed herein may have various componentscollocated; however, it should be appreciated that the components of thearrangements may be combined into one or more apparatuses. In someinstances, well-known features are omitted or simplified to clarify thedescription of the exemplary implementations. While a particular featureof the disclosure may have been disclosed with respect to only one ofseveral implementations, such feature may be combined with one or moreother features of the other implementations as may be desired andadvantageous for any given or particular application.

As used herein, the word ‘exemplary’ means serving as an example,instance, or illustration. Any aspect or design described herein as‘exemplary’ is not necessarily to be construed as preferred oradvantageous over other aspects or designs. Rather, use of the wordexemplary is intended to present concepts and techniques in a concretefashion. The term ‘techniques’, for instance, may refer to one or moredevices, apparatuses, systems, methods, articles of manufacture, and/orcomputer-readable instructions as indicated by the context describedherein.

As used herein, the articles ‘a’ and ‘an’ should generally be construedto mean ‘one or more,’ unless specified otherwise or clear from contextto be directed to a singular form.

As used herein, the terms ‘coupled’ and ‘connected’ may have been usedto describe how various elements interface. Unless expressly stated orat least implied otherwise, such described interfacing of variouselements may be either direct or indirect.

As used herein, the terms ‘having’, ‘containing’, ‘including’, ‘with’ orvariants thereof, and like terms are open ended terms intended to beinclusive. These terms indicate the presence of stated elements orfeatures, but do not preclude additional elements or features.

As used herein, the word ‘continuous’ is to be understood in contextwith an implemented mode of operation. For example, if a system isunderstood to operate in a clocked mode, the wording ‘continuousoperation’ can mean an operation in the clocked mode while the wordingdoes not address operation in another mode. For another example, if asystem is described to operate in an active mode and not to operate inan inactive mode, ‘continuous operation’ can mean continuous operationin the active mode and no operation while the system is in the inactivemode. As used herein, the wording ‘to perform continuously’ is notnecessarily to be understood as unconditionally ‘always’. Conditionssuch as a prerequisite for a certain continuous mode of operation can bedefined to be met as a requirement for a continuous performance. Thecontinuous performance can be defined to last as long as the conditionsare met. One condition can be activation of a continuous mode ofoperation having a predetermined condition for deactivation such ascompletion of a predetermined duration.

As used herein, various links, including communications channel,connecting the elements can be wired or wireless links, or anycombination thereof, or any other known or later developed element(s)that is capable of supplying and/or communicating data to and from theconnected elements.

As used herein, the terms ‘determine’, ‘calculate’ and ‘compute’, andvariations thereof, are used interchangeably and include any type ofmethodology, process, mathematical operation or technique. As usedherein, the wording ‘A coupled to B’ means a capacity of A to provide Cto B, provided that B is ready to accept C, wherein C, as the case maybe, is a signal, power, message or other abstract or concrete thing asdescribed in the context of the wording.

As used herein, directional terminology, such as ‘top’, ‘bottom’,‘front’, ‘back’, ‘leading’, ‘trailing’, etc., is used with reference tothe orientation of the figure(s) being described.

As used herein, terms such as ‘first’, ‘second’, and the like, are alsoused to describe various elements, regions, sections, etc. and are alsonot intended to be limiting.

What is claimed is:
 1. A method comprising: placing a wafer on areceptacle comprising a chuck base, wherein a light port for emittinglight from a source of light is an opening located in a surface of thechuck base, and wherein the light port is located underneath the wafer;shining the light from the light port at an edge of the wafer so thatlight passes by the edge of the wafer; and processing the wafer on thereceptacle based on the light that passed by the edge of the wafer andthat is received by a light sensitive element.
 2. The method of claim 1,wherein the chuck base comprises a rotation axis and a rim along acircumference of the chuck base, and wherein the light port is locatedbetween the rim and the rotation axis.
 3. The method of claim 2, whereinthe rim extends towards the wafer.
 4. The method of claim 3, wherein thelight port is located closer to the rim than to the rotation axis. 5.The method of claim 4, wherein the light port comprises a plurality oflight ports, each light port spaced apart equidistantly from anotherlight port.
 6. The method of claim 1, further comprising a turntable,wherein the turntable is located between the wafer and the chuck base.7. The method of claim 6, wherein processing the wafer comprises:detecting, by the light sensitive element, the light that passed by theedge of the wafer; generating, by a controller, position datarepresenting information about a position of the wafer based on thedetected light; instructing, by the controller, a driver to move theturntable to an adjusted position; and moving, by the driver, theturntable and thereby the wafer to the adjusted position.
 9. A methodcomprising: placing a wafer on a receptacle, wherein the wafer has anupper long side and a lower long side, and wherein the upper long sideis connected to the lower long side by an outer edge; shining light froma light port at the outer edge of the wafer so that the light passes bythe outer edge of the wafer, wherein the light port is located at asurface of the receptacle; and processing the wafer on the receptaclebased on the light that passed by the outer edge of the wafer and thatis received by a light sensitive element.
 10. The method of claim 9,wherein the light port is an opening located in the surface of thereceptacle.
 11. The method of claim 9, wherein the receptacle comprisesa chuck base.
 12. The method of claim 11, wherein the receptacle furthercomprises a turntable arranged between the wafer and the chuck base. 13.The method of claim 11, wherein the chuck base comprises a rotation axisand a rim along a circumference of the chuck base, and wherein the lightport is located between the rim and the rotation axis.
 14. The method ofclaim 13, wherein the rim extends towards the wafer.
 15. The method ofclaim 14, wherein the light port is located closer to the rim than tothe rotation axis.
 16. The method of claim 15, wherein the light portcomprises a plurality of light ports, each light port spaced apartequidistantly from another light port.
 17. The method of claim 9,wherein the light port emits light of a light emitting diode.
 18. Themethod of claim 9, wherein processing the wafer comprises: detecting, bythe light sensitive element, the light that passed by the outer edge ofthe wafer; generating, by a controller, position data representinginformation about a position of the wafer based on the detected light;instructing, by the controller, a driver to move the receptacle to anadjusted position; and moving, by the driver, the receptacle and therebythe wafer to the adjusted position.